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25.8mm bars in a 25.4mm stem - ok or not?

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25.8mm bars in a 25.4mm stem - ok or not?

Old 06-23-09, 07:25 AM
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meanwhile
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25.8mm bars in a 25.4mm stem - ok or not?

And what about 26mm, for that matter? Is this just a matter of tightening and allen bolt less or a serious safety issue?
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Old 06-23-09, 07:46 AM
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Google for: handlebar shim

Doh! Didn't read carefully, and now see the situation is the reverse of what uses a shim.

Last edited by Shimagnolo; 06-23-09 at 10:06 AM.
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Old 06-23-09, 09:59 AM
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no, you can't jam a bigger diameter object into a smaller diameter clamp, it doesn't work.
you can insert smaller diameter object into larger diameter clamp, but you have to use shims.

this comes up quite often, same answer, no, unless you have a good dental plan.

25.8mm and 26mm are the same thing. 26mm bars rarely have a diameter of 26mm, closer to 25.9mm.

it's essentially the same thing as trying to get a 27.2mm seatpost into a 26.8mm seat tube.
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Old 06-23-09, 11:16 AM
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Originally Posted by AEO View Post
it's essentially the same thing as trying to get a 27.2mm seatpost into a 26.8mm seat tube.
A clamp needs tightening and will go wider than the bars - a tube won't. So I'm not sure the analogy is a good one. A reasonably respected British bike store says that a 25.8mm bar WILL work in a 25.4 stem - https://www.sjscycles.co.uk/product.a...40&src=froogle
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Old 06-23-09, 11:28 AM
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And this what the wikipedia article on stems says:

Handle bar diameter

Both quill and threadless stems come in a variety of bicycle handlebar clamp diameters. The ISO standard for the clamping area of a handlebar is 25.4 mm (1"), which is used on mountain bikes and many Japanese-made road handlebars. However, the Italian unofficial standard is 26.0 mm, which is the most common clamp size for road bars. There are also intermediate sizes such as 25.8 mm to try and achieve compatibility with either an ISO or Italian stem, and the old Cinelli-specific size of 26.4 mm. In practice, many modern stems with removable faceplates allow for slight differences in handlebar clamp diameter, but the older type of stem with a single pinch bolt must be accurately matched.
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Old 06-23-09, 11:31 AM
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facepalm

if you have those search skills, you could have pulled up all the info here in BF mechanics.
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Old 06-23-09, 11:33 AM
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It's the difference of 1/64th of an inch. Depending on the manufacturing tolerances of the bar and stem, you might get a little more or less difference. If you don't care too much about the finish on the bars you can sand off 1/64th of an inch with some fine grit sandpaper to make the clamp area on the bars the right nominal diameter. Even if the bars and stem matched, the clamp opens much more than that much to get the bars in and out. It'll be fine, but might take a bit of extra force.
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Old 06-23-09, 09:28 PM
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bah! you CAN jam 26mm bars in your 25.4 stem! i've done it (currently). it sucks to get it on though (haven't tried getting them off), and you will scratch up your bars, but who cares imo. you might want to grease it up a little to help slide it on.
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Old 06-23-09, 11:17 PM
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Depends on the stem type you have. Do you have a one-bolt stem clamp? If you do, though, illwafer said it - maybe it'll work but it'll be a pain and you'll scratch things up.

If you have a two-bolt or four-bolt stem clamp with a removable face plate, then you have a better option - you can easily remove a bit of material from the face plate and possibly the receiver part of the stem and have it fit great. Of course, such modifications are more safely done on heavy overengineered steel stems than they are on lightweight aluminium stems. In fact, I wouldn't consider doing it to a lightweight aluminium stem.
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Old 06-24-09, 01:20 PM
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Originally Posted by AEO View Post
facepalm

if you have those search skills, you could have pulled up all the info here in BF mechanics.
At the moment BF barely works for me at all - and sometimes it jams completely. I've completely given up on doing searches here. I was assuming it was like this for everyone...?
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Old 06-24-09, 01:29 PM
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I get slow responses from the server both at work and at home. But it isn't slow enough to mess with a search.
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Old 06-24-09, 01:34 PM
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I wouldn't do it, personally. You should consider using a brake cylinder hone and a drill to remove some material IMHO.
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Old 06-24-09, 02:21 PM
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add "site:www.bikeforums.net" to the search parameter in google to search through BF.
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Old 06-24-09, 02:34 PM
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Originally Posted by meanwhile View Post
At the moment BF barely works for me at all - and sometimes it jams completely. I've completely given up on doing searches here. I was assuming it was like this for everyone...?
Search still works for me, just be sure to check the box to sort by relevance.
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Old 06-24-09, 03:24 PM
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Originally Posted by AEO View Post
add "site:www.bikeforums.net" to the search parameter in google to search through BF.
I do that now as well.
Had lost my patience many times before I figured that one out.

And as illwafer said: it can be done, I've done it too, it'll cause scratches, use grease, etc...
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Old 06-24-09, 04:14 PM
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A run-of-the-mill stem costs what? Maybe $20.00? If you're worried enough to ask I'd spend the money to get a stem with the right clamp size. When I rework a bike for personal use, I almost always wind up buying a stem so that I can tailor the bike fit to suit me anyway. Another alternative would be to buy a handlebar that has a clamp diameter that matches your stem.

Having said that, if it was my bike and I already owned both the stem and the handlebar, I might do it. Carbon handlebar, definitely not. Lightweight aluminum bar, definitely not. Garden variety aluminum bar, I might try it but I wouldn't just stick it in and tighten the face plate.

Look at where your face plate meets the body of the stem. See those nice square edges on the top and bottom of the clamp? They are going to dig furrows into your handlebar and create stress risers. Think of how easy it is to tear a piece of cloth once you make a tiny cut in one of the edges. Before installing the handlebar I'd chamfer all four of those edges with a file or grinder.
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